Detailed explanation of the causes of LED junction temperature

For most people, “LED junction temperature” is not yet familiar, but even for those in the LED industry, it is not that well-known! Now let’s explain in detail. When LED is working, the following situations can cause the junction temperature to rise to varying degrees.
1、 After multiple practices, it has been proven that the limitation of light output efficiency is the main reason for the increase in LED junction temperature. At present, advanced material growth and component manufacturing processes can convert a large portion of the input electrical energy of LEDs into light radiation energy. However, due to the much larger refractive index of LED chip materials compared to the surrounding medium, a large portion of photons (>90%) generated inside the chip cannot smoothly overflow the interface, and undergo total reflection at the interface between the chip and the medium. After multiple internal reflections, they are finally absorbed by the chip material or substrate and become heat in the form of lattice vibration, causing the junction temperature to rise.
2、 Due to the fact that the P-N junction cannot be extremely perfect, the injection efficiency of the component will not reach 100%. In other words, during LED operation, in addition to injecting charges (holes) from the P region to the N region, the N region will also inject charges (electrons) into the P region. Generally, the latter type of charge injection does not produce photoelectric effects and is consumed in the form of heat. Even if the useful part is injected with charges, it will not all turn into light. Some of it will combine with impurities or defects in the junction region and eventually become heat.
3、 The electrode structure with poor components, the material of the window layer substrate or junction region, and conductive silver paste all have certain resistance values, which are stacked against each other to form the series resistance of LED components. When current flows through the P-N junction, it also flows through these resistors, generating Joule heat and causing an increase in chip temperature or junction temperature.
The above are the main reasons for the junction temperature of LED, and of course, other factors cannot be ruled out. Of course, we cannot understand the chemical or physical phenomena involved yet, but in the near future, with the continuous progress of science and technology, we will be able to better explain these phenomena. Science will use its magic to unravel our doubts one by one!